In order to wrap a measurement air bladder around a body part to be measured at an appropriate strength, conventional blood pressure measurement devices preliminarily inflate the measurement air bladder at the start of measurement of blood pressure.
The measurement air bladder is embedded in a measurement cuff together with, for example, a compression air bladder, which is one example of a means to compress the measurement air bladder. Blood pressure is measured based on changes in the pressure of the measurement air bladder.
The aforementioned preliminary inflation is disclosed in, for example, Patent Literature 1 (JP 2005-305028A). According to Patent Literature 1, after a predetermined amount of air is supplied to a measurement air bladder, the rate of increase in the pressure of a compression air bladder is detected while increasing the pressure of the compression air bladder. Following the start of the pressure increase, a process of wrapping the measurement air bladder is completed when a predetermined rate of increase in the pressure is detected.
Measurement of blood pressure based on changes in the pressure of a measurement air bladder is disclosed in, for example, Patent Literature 2 (JP S62-268532A). More specifically, pressure pulse waves (changes in the internal pressure of the measurement air bladder) with amplitudes corresponding to thresholds (Th_SBP and Th_DBP) with respect to the maximum pressure pulse wave value are calculated as pressure values. Note that these thresholds are detected using the following Expressions 1 and 2. Note that in the following Expressions 1 and 2, AmpMax is the maximum pressure pulse wave amplitude value, and αSBP, βSBP, αDBP and βDBP are constants that are obtained experimentally.Th_SBP=AmpMax×αSBP+βSBP   (Expression 1)Th_DBP=AmpMax×αDBP+βDBP   (Expression 2)
Patent Literature 1: JP 2005-305028A
Patent Literature 2: JP S62-268532A